1. Field of the Invention
This invention relates to a valve which automatically shuts off the flow of combustible gas from a ruptured conduit or failed fitting.
2. Description of Prior Art
Conventional combustible distribution systems bring gas from a street main below ground level, through a tapping tee, a service line, a riser above ground level, a meter cock, a regulator, a meter and then into the customer""s structure.
Rupture of the line or failure of fittings between the consumer property line and the served customer structure can occur for any number of reasons. Among these are digging by the customer or other party, ground settling, failure of a regulator, failure of a meter, failure of fittings and earthquakes. Rupture of the line or failure of fittings can also occur on the inside customer fuel gas piping or flexible connection. Dangerous explosive conditions can arise when any such rupture occurs.
Prior art patents show various structures for shutting off the gas flow when the flow exceeds a predetermined value, e.g. due to the downstream rupture. These include automatic excessive flow valves (EFV) separated from a manual shut off valve near the gas main and downstream of the tapping tee or a combination of an EFV and manual shut-off valve in a single unit. Separate valves require installing the excessive flow valve and the shut-off valve at two locations which has certain apparent disadvantages, including more work for the installer or plumber and consequently greater cost, and the need to provide twice as many connection points with, consequently, twice as many locations for potential leakage, i.e. four connection points instead of two connection points. By combining the EFV and manual shut-off valve in a single unit these disadvantages are overcome. Further, the resultant device can be used where the gas service line inside the home or other structure connects to an appliance such as a gas dryer, oven, furnace, water heater or fireplace.
U.S. Pat. No. 6,003,550 (""550) combines two such separate valves by incorporating an EFV in a rotative shut-off valve member. However, the EFV of ""550 and those conventional EFV""s separate from the manual shut off valve are all more complicated than that of the valve according to the invention.
An object of the invention is directed to a unique and improved EFV which can be used either as an EFV separated from a manual shut off valve by inserting the EFV into a valve housing, section of pipe, other system flow area component or into a ball of a manual shut-off valve. Such insertion requires minimal modification of the to accept the EFV according to the invention for permanent installation.
The modular design of the EFV affords easy and inexpensive installation requiring no additional hardware for operation.
The EFV according to the invention comprises a tripod which aids stability, and its retention features in the valve housing, pipe or ball of the manual shut-off valve double as the EFV seat for the shut-off disk of the EFV.
Unlike constructions employing snap rings, threads, and the like on which debris accumulates, minimal surfaces are presented by the EFV according to the invention for such accumulation.
The EFV according to the invention can also be easily reset by simply closing the corresponding shut-off valve.
The spring design and low weight of the EFV according to the invention maximize a small change in trip flow due to orientation.
The EFV is also superior to gravity operated valves because of orientation independence; and it is superior to magnet designs because a magnetic float is subject to clogging as debris tends to gather at the magnet of such float.
The above objectives are achieved by an improved excess flow valve according to the invention inserted into a valve housing, section of pipe or other system flow area component separate from the corresponding manual shut-off valve or inserted into a rotatable stopcock of a shut-off valve.
The separated EFV valve according to the invention comprises an outer body or housing (preferably formed of brass) formed in a separate valve housing (which may be a section of pipe) having a bore extending therethrough which serves as a gas passageway and retains the improved EFV according to the invention. The combined EFV and manual shut-off valve has a cavity along the gas passageway in which a rotatable ball resides having a bore extending therethrough which can be aligned with the gas passageway. The ball carries a stem which extends through the brass housing on which a rotatable handle is engaged, so that the ball can be rotated within the cavity to an xe2x80x9conxe2x80x9d position, in which the bore through the ball aligns with the passageway, or to an xe2x80x9coffxe2x80x9d position 90xc2x0 from the xe2x80x9conxe2x80x9d position, wherein the ball blocks the gas passageway.
Fitted within either the bore of the valve housing or the bore of the ball of the combined valves is the improved excess flow valve (EFV) according to the invention. This EFV is formed primarily of a rigid polymer material, comprising a tubular supporting body having three supporting struts extending out from the tubular supporting body and spaced at 120xc2x0 from one another forming a tripod configuration. The tubular supporting body of the EFV has an axial bore extending therethrough and a spring biased stem movable axially within the bore having a nose which extends outwardly from the downstream end of the supporting body which carries a soft disk which is seatable on a shoulder within the bore of a separate EFV valve or the ball of the combined valves to close the excess flow valve upon a drop in pressure downstream from the valve.
Should service be required on an appliance served by the improved EFV according to the invention, or if for some reason it were necessary to manually shut off the gas to the appliance, the corresponding shut-off valve can be manually turned to the off position to accomplish this result. In operation, the stem of EFV is spring biased opposite to the direction of flow. Under normal conditions the disk on the stem is held away from a valve seat by the bias spring. When the flow is excessive, such as when the service line ruptures downstream of the EFV, the forces from the flowing fluid overcome the spring bias and the disk closes against the seat, shutting off the flow. Thus, the dangerous flow of combustible gas is stopped.